Clipping of a PICA Aneurysm Located on the Contralateral Side of Its Parent Vertebral Artery in Front of the Brainstem: How I Do It

Acta Neurochirurgica (2019) 161:1529–1533 https://doi.org/10.1007/s00701-019-03967-5

HOW I DO IT - VASCULAR NEUROSURGERY - ANEURYSM

Clipping of a PICA aneurysm located on the contralateral side of its parent vertebral artery in front of the brainstem: how I do it

Michel W. Bojanowski1 & Pascale Lavoie2 & Elsa Magro3,4

Received: 2 March 2019 /Accepted: 29 May 2019 /Published online: 28 June 2019 # Springer-Verlag GmbH Austria, part of Springer Nature 2019

Abstract Background Vertebro-PICA aneurysms may be challenging because of their relationship with the brainstem and the lower cranial nerves, especially when the vertebral artery is tortuous and the aneurysm is located in front of the brainstem, contralaterally to the parent vertebral artery. We describe the surgical technique for safe approach. Method Cadaveric dissection performed by the authors, provided comprehensive understanding of relevant anatomy. Intraoperative photos and videos show clipping of the aneurysm using a combined midline and far-lateral suboccipital craniotomy with a para-condylar extension. The literature reviews potential complications. Conclusion This combined approach allows safe clipping of such PICA aneurysms.

Keywords PICA aneurysms . Contralateral approach . Far-lateral approach . Para-condylar extension

Relevant surgical anatomy occipital bone, which form the lateral wall of the foramen magnum [7]. This latter part is the area we wish to focus on. The occipital bone surrounding the foramen magnum has The lateral wall of the foramen magnum is composed of the three parts. The inferior portion of the clivus forms its anterior occipital condyle, the jugular tubercle, and the jugular process wall, the squamous portion its posterior wall, and both these (Fig. 1). The occipital condyle is located on the lateral side of parts are united on each side by the condylar parts of the the anterior portion of the foramen magnum, extending infe- riorly. Directly above at the junction of the middle and poste- This article is part of the Topical Collection on Vascular Neurosurgery - rior thirds of the occipital condyle is the hypoglossal canal, Aneurysm which allows the hypoglossal nerve to exit the skull in an Electronic supplementary material The online version of this article anterolateral direction (Fig. 1a). The roof of the hypoglossal (https://doi.org/10.1007/s00701-019-03967-5) contains supplementary canal is the jugular tubercle, which is a bony outgrowth of the material, which is available to authorized users. occipital bone, located at the anteromedial aspect of the jugular foramen. Extending posteriorly from the jugular tubercle * Michel W. Bojanowski and forming the postero-medial wall of the jugular foramen is [email protected] the jugular process (Fig. 1b, c). The sigmoid sinus enters the Pascale Lavoie posterior end of the jugular foramen to connect with the jug- [email protected] ular bulb (Fig. 1a). Thus, the jugular process is the bone located between the sigmoid sinus, laterally, and the foramen Elsa Magro [email protected] magnum, medially. The most posterior extension of the jugular process corresponds extra-cranially to the condylar fossa, 1 Division of Neurosurgery, Centre Hospitalier de l’Université de located directly behind the occipital condyle. It is in the con- Montréal, 1051 Sanguinet street, Montreal, QC H2X 3E4, Canada dylar fossa that the posterior condylar foramen may at times 2 Division of Neurosurgery, CHU de Quebec, Hôpital l’Enfant Jésus, be found, connecting the vertebral venous plexus to the sig- Quebec, Canada moid sinus via the posterior condylar emissary vein [6]. In 3 Department of Neurosurgery, University Hospital of Brest, cases where the posterior condylar foramen is present, it is a Brest, France landmark limiting lateral drilling of the condylar fossa, past 4 LaTIM, INSERM, UMR 1011, Paris, France which is the sigmoid sinus. 1530 Acta Neurochir (2019) 161:1529–1533

Fig. 1 Cadaveric dissection. a Posterior view of the cranio- cervical junction illustrating the bone landmarks and the neurovascular structures. b After resection of the occipital condyle and the jugular process. c After opening the dura of the jugular foramen

The occipital condyle is jointed to the lateral mass of C1 2c). In the groove of C1, surrounding the VA there is a venous (Fig. 2a). Postero-medially to this joint, the VA passes in the plexus, which is in continuity with the suboccipital venous groove of C1 and turns sharply anteriorly, just medial to the plexus [2](Fig.2b). The venous plexus itself, surrounding the joint, to enter the dura and continue intracranially (Figs. 1a and VA, is surrounded by a fibrous periosteal ring [2].

Fig. 2 Cadaveric dissection, view of a right side in operative position. a Bone landmarks. b After suboccipital craniotomy. c After resecting the occipital condyle and the jugular process Acta Neurochir (2019) 161:1529–1533 1531

Description of the technique groove in which the VA passes, making sure to keep the periosteal sheet intact to avoid bleeding from the sinus surround- Positioning In order to have access to its neck, the aneurysm ing the VA(Fig. 3b). At this point, the VAis identified where it needs to be approached from the same side on which it is enters intradurally. On the medial side, the suboccipital bone located, and not from the side of the origin of its parent artery. and the posterior arch of C1 are exposed past the midline (Fig. The patient is placed in park-bench position, with the aneu- 3b). rysmal side facing up (Fig. 3a). The head is flexed with the chin 1 cm from the sternum, and the nose in line parallel to the Bone resection A suboccipital craniotomy is performed, from floor. Subsequently, the head is flexed laterally, about 20°, on the inferior nuchal line superiorly, all the way to the foramen the opposite side of the site of the surgery. magnum, extending past the midline (Fig. 3b). On the lateral side, the sigmoid sinus is exposed (Fig. 3b).Theboneofthe Monitoring Electrodes on the tongue assess the hypoglossal condylar fossa, which is located behind the occipital condyle, nerve, two on the face assess the upper and lower components is removed. The posterior portion of the occipital condyle of the facial nerve, and electrodes on the endotracheal tube itself is drilled, no more than its medial one third, to preserve assess the mixed nerves. the joint with C1 (Fig. 3c). Part of the jugular process is drilled, exposing the jugular bulb and allowing for better ma- Skin incision and bone exposure It is necessary to expose both neuverability when accessing the anterolateral aspect of the sides of the brainstem: the side on which the aneurysm lies to brainstem. The posterior arch of C1 is removed, laterally as far allow clipping, as well as the opposite side to have proximal as the VA and medially, past the midline (Fig. 3c). control of the parent artery given that the narrow window surrounding the aneurysm does not allow placement of a tem- Intradural dissection and clipping The case of a patient with a porary clip just proximal to it. We use a hook-shaped incision, left PICA aneurysm lying on the right side of the anterior starting on the midline from C2 to the inion, and then curving aspect of the medulla is illustrated in the supplementary video towards the tip of the mastoid (Fig. 3a). We cut through all the and Figs. 3 and 4. layers of the muscles, making one single flap, followed by elevation of the periosteum to expose the suboccipital area. At the level of the inion, a margin of muscle is left attached to Indications the bone, to facilitate the approximation of the muscles during closure. On the lateral side, the condylar fossa and the occip- Vertebro-PICA aneurysms (VPa), located anterior to the ital condyle is exposed. The posterior condylar emissary vein brainstem, past the midline, on the contralateral side of the is coagulated. At C1, the periosteum is elevated past the parent vertebral artery (VA).

Fig. 3 Case illustration. a Positioning. b After suboccipital craniotomy. c After removing the bone of the condylar fossa. d After opening the dura 1532 Acta Neurochir (2019) 161:1529–1533

Fig. 4 Case illustration. a and b Head angio-CT scan, axial slice, pre- and Cerebral angiogram of the left vertebral artery, anteroposterior (c and d) postoperatively, respectively, showing the location of the VPa on the and anterolateral (e and f) views, showing the contralateral position of the contralateral side (a), the condylar resection, and the clipping (b). c–f VPa preoperatively (c and e) and his exclusion after clipping (d and f)

Limitations Information to patient

– Location of the aneurysm (height along the VA and pro- Injury to mixed CNs may require tracheostomy and jection towards the anterior brainstem) determines the gastro-jejunostomy. amount of bone to be removed [1, 3, 9, 10]. Pain related to exposure. – When aneurysm is high on the VA, a posterior petrosectomy may be required. Compliance with ethical standards

Conflict of interest The authors declare that there are no conflicts of How to avoid complications interest.

– Identification of the VA overlying C1 before drilling the condyle – Drilling no more than 1/3 of the condyle to avoid References occipito-vertebral instability – 1. Brag TM, Duckworth EAM (2008) Contralateral far-lateral ap- Sufficient lateral bone removal to minimize manipulation proach for clipping of a ruptured vertebral artery-posterior inferior of neural structures cerebellar artery aneurysm. Neurosurg Focus 25(6):E9 – Monitoring of lower CNs 2. Campero A, Rubino P, Rhoton AL. Anatomy of the vertebral artery. – Minimizing the use of brain retractor In Bruneau,George, Spetzler, eds. Pathology and Surgery around the Vertebral Artery. Paris: Springer; 2011:29–40 – Assessing the quality of clipping using intraoperative an- 3. Kawase T, Bertalanffy H, Otani M, Shiobara R, Toya S (1996) giography or ICG, when available Surgical approaches for vertebro-basilar trunk aneurysms located – Careful closure to avoid CSF leakage in the midline. Acta Neurochir 138(4):402–410 4. Matsushima T, Natori Y, Katsuta T, Ikezaki K, Fukui M, Rhoton AL (1998) Microsurgical anatomy for lateral approaches to the Specific perioperative considerations foramen magnum with special reference to transcondylar fossa (supracondylar transjugular tubercle) approach. Skull Base Surg 8(3):119–125 Assessing integrity of mixed CNs: 5. Matsushima T, Matsukado K, Natori Y, Inamura T, Hitotsumatsu T, Fukui M (2001) Surgery on a saccular vertebral artery-posterior inferior cerebellar artery aneurysm via the transcondylar fossa Patient must be fully alert before extubation to avoid (supracondylar transjugular tubercle) approach or the transcondylar pulmonary aspiration approach: surgical results and indications for using two different Swallowing fully assessed before oral feeding lateral. J Neurosurg 95(2):268–274 Acta Neurochir (2019) 161:1529–1533 1533

6. Matsushima K, Funaki T, Komune N, Kiyosue H, Kawashima M, - Occipito-vertebral joint Rhoton AL (2015) Microsurgical anatomy of the lateral condylar - Dominance of the sigmoid sinus vein and its clinical significance. Neurosurgery 11(Suppl 2):135– 145 discussion 145–6 - Size of the condylar emissary vein 7. Rhoton AL (2000) The foramen magnum. Neurosurgery 47(3 - Dominance of the VA Suppl):S155–S193 • Avoiding venous congestion by proper positioning and anesthetic 8. Rohde V, Schaller C, Hassler W (1994) The extreme lateral management transcondylar approach to aneurysms of the vertebrobasilar junc- • Early identification of the extradural VA before drilling the occipital tion, the vertebral artery, and the posterior inferior cerebellar artery. condyle – Skull Base Surg 4(4):177 180 • Partial resection of the occipital condyle and the jugular process, and 9. Taguchi Y, Hoshikawa Y, Tanaka K, Miyakita Y, Morishima H, when necessary of the jugular tubercle [4,5, 6X, 8, 11] according to the Sekino H (1996) Contralateral transcondylar approach for aneu- projection of the aneurysm towards the anterior brainstem rysms of the posterior inferior cerebellar artery-vertebral artery • Sufficient exposure almost always achieved by partial drilling of the complex. J Clin Neurosci 3(2):156–161 occipital condyle while sparing the articular facet 10. Troude L, Bernard F, Sy ECN, Roche PH (2019) The modified • retrosigmoid approach: a how I do it. Acta Neurochir 161(2):417– Neuronavigation to assist in locating occipital condyle and aneurysm 423 • Proximal control by exposure of the parent VA on the contralateral 11. Wen HT, Rhoton AL, Katsuta T, de Oliveira E (1997) Microsurgical side of the aneurysm anatomy of the transcondylar, supracondylar, and paracondylar ex- • Minimal manipulation of CNs and brainstem tensions of the far-lateral approach. J Neurosurg 87(4):555–585

Key points• Masterful knowledge of the anatomy and variants of the lateral wall of the foramen magnum and its surrounding neurovascular structures Publisher’snote • Springer Nature remains neutral with regard to Use of high-quality imaging to enable thorough pre-operative jurisdictional claims in published maps and institutional affiliations. planning • Particular structures to look out for with the use of imaging: